The present invention relates to an improved grain quality analyzer and, more particularly, to a grain quality analyzer which includes photo-optical means for measuring the optical characteristics of a sample, and control and computing means for computing the percentage concentration of selected constituents in the grain sample.
The value of agricultural grain commodities, such as wheat, corn, soy beans, and the like, from both the economic and nutritional standpoints, is partly determined by the percentage concentration of protein and moisture. Consequently, it is desirable for those in the production, sale, and distribution of grains to have means for quickly and accurately measuring the percentage concentration of these constituents. It is known, for example, to determine these percentages by laboratory-type chemical analysis, an accurate but time consuming procedure, and by use of a photo-optical grain quality analyzer. Grain can be optically analyzed because certain optical characteristics of the grain, principally the optical density (OD), transmissivity, reflectivity, and absorption vary at certain wavelengths of light as a function of the concentration of protein, oil, and moisture.
A commercially available photo-optical grain quality analyzer is disclosed in the above referenced U.S. patents which are assigned to the assignee of the present invention. This instrument uses photo-optical techniques to obtain optical density values which are a function of the percentage concentrations of the protein, oil, and moisture and includes computation circuitry to compute the actual percentage concentration in accordance with known equations. A sample of the grain to be analyzed is irradiated with filtered light which passes from an infrared light source through a rotatable filter wheel to the grain sample. The filter wheel includes a plurality of radially extending filters, each of which is designed to pass light at a selected wavelength. As the filter wheel rotates, each filter is successively introduced into the irradiating light and caused to pass filtered light energy at wavelengths which sweep across a selected bandwidth from a first wavelength to a second wavelength in the infrared spectrum. The cumulative effect of the plural filters of the filter wheel is to irradiate the sample with light, the wavelength of which sweeps, in serially adjacent bandwidths, across a substantial portion of the infrared spectrum. The irradiating light includes selected wavelengths which are known to be of value in determining the percentage concentration of the measured constituents and, specifically, are those light wavelengths at which the optical characteristics of the sample, viz., the optical density (OD), reflectivity, transmissivity, and/or absorption, are known to vary as a function of the concentration of the measured constituent. In the reflectance mode of operation, photo-responsive devices are positioned with respect to the sample such that they measure the light reflected from the sample as the wavelength varies. This reflected light, which is inversely proportional to the optical density (OD) of the sample, is used to provide a measure of the optical density of the sample at a selected wavelength and a measure of the change in the optical density (that is, the .DELTA.OD) as the wavelength of the light is swept across the infrared spectrum.
The above described grain quality analyzer employs equations relating to the non-destructive photo-optical testing of agricultural products in which the reflective optical density is measured by the reflectivity R and is defined by the following equation: EQU OD=Log(1/R) EQ. 1
In this equation, the reflectivity, R, is a ratio of the intensity of the reflected light to the intensity of the incident light at the selected wavelength: EQU R=(I.sub.r /I.sub.i) EQ. 2
The change in the optical density between two wavelengths (that is, across a selected bandwidth) is given by the following equation: EQU .DELTA.OD=Log(I.sub.i /I.sub.r).sub.1 -Log(I.sub.i /I.sub.r).sub.2 EQ. 3
The subscripts 1 and 2 represent the first and second wavelengths. If the intensity of the irradiating light is approximately the same at both wavelengths, then the above equation reduces to: EQU .DELTA.OD=Log(I.sub.r).sub.2 -Log(I.sub.r).sub.1 EQ. 4
Consequently, the differences between the common log of the intensity of the reflected light is an indication of the change in the optical density.
The instrument employs control circuitry to obtain the .DELTA.OD measurement at wavelengths which are known to vary as a function of the concentration of the protein, oil, and moisture and employs computational circuitry to compute the actual percentage concentration using the following three equations: EQU oil %=K.sub.0 +K.sub.1 (.DELTA.OD).sub.w +K.sub.2 (.DELTA.OD).sub.o +K.sub.3 (.DELTA.OD).sub.p EQ. 5 EQU water %=K.sub.4 +K.sub.5 (.DELTA.OD).sub.w +K.sub.6 (.DELTA.OD).sub.o +K.sub.7 (.DELTA.OD).sub.p EQ. 6 EQU protein %=K.sub.8 +K.sub.9 (.DELTA.OD).sub.w +K.sub.10 (.DELTA.OD).sub.o +K.sub.11 (.DELTA.OD).sub.p EQ. 7
In these three equations, K0-K11 are constants or "influence factors" and the subscripts W, O, and P indicate the characteristic wavelengths which are associated with the change in optical density measurements for these constituents. As indicated above, the characteristic wavelengths are those wavelengths at which the optical characteristics of the sample are sensitive to or vary with the percentage concentrations of water, oil, and protein.
The above described grain quality analyzer performs the necessary computations, both as to the .DELTA.OD measurements and to the equations set forth above, by using electronic control and computation circuitry, including both analog and digital circuits. While the percentage concentration of the protein, oil, and moisture can be accurately determined, inaccuracies can occur because of the relatively large number of constants, K0-K11, which must be accurately determined and maintained in the computation circuitry, and the adverse effect of light scattering from sample to sample. The inaccuracies introduced into the measuring process by light scattering can be minimized, but not entirely eliminated, by preparing each grain sample in a consistent, uniform manner, e.g., by grinding the grain sample into uniformly sized particles.
Research efforts have been undertaken for the purpose of uncovering other, simpler equations for use in photo-optical instruments by which the percentages of the selected constituents can be photo-optically determined while maintaining or improving the accuracy of the measurement. One researcher, Mr. K. H. Norris, of the U.S.D.A. Agricultural Research Service in Greenbelt, Md., has empirically arrived at the following simplified equation for measuring the percentage concentration of protein in a grain sample: ##EQU1## When compared to the protein equation employed by the above described grain quality analyzer (EQ.7), this equation utilizes two rather than four of the twelve influence factors and a reflectivity ratio obtained from the sample. The reflectivity values, R.sub.1 and R.sub.2, of the numerator and denominator represent, respectively, the reflectivity of the sample at two spaced points in the range of characteristic wavelengths and two spaced points in the range of neutral wavelengths. As explained above, the characteristic wavelengths for protein are a range of wavelengths in which the optical characteristics of the sample, in this case, the reflectivity, are sensitive to or vary as a function of the percentrage concentration of the protein, and the neutral wavelengths are those wavelengths at which the optical characteristics of the sample are not sensitive to or are independent of the percentage concentration of the measured constituent.
The use of a ratio of optical characteristics in determining the percentage concentration of a constituent was previously employed by Mr. Norris in photo-optically measuring the percentage contents of fat in ground meat as disclosed in U.S. Pat. No. 3,877,818, issued Apr. 15, 1975.
The present inventor, in an effort to further simplify the percentage protein determination, has derived a further equation which further simplifies the determination of the percentage protein and which is more compatible with less sophisticated, less expensive computational electronics.